The invention relates to a stirring arrangement with a rotating stirring body for stirring fluids, with stirring blades attached to a stirring body hub. The stirring device also includes a gas supply device which supplies a gas, such as air, for dispersing with the stirring body.
In many chemical reactors or bioreactors with a stirring arrangement, reactions occur wherein at least one reaction partner is present as a gaseous starting component. The stirring arrangement is provided to finely distribute the gaseous component and to thus provide a large boundary surface between the gaseous component or the fluid such that the gaseous component goes at least partially or entirely into solution and takes part in the reaction progressing in the reactor.
Accordingly, there are applications where the stirring arrangement must disperse a gas. The task of dispersing a gas occurs in practice mostly in conjunction with additional primary tasks, for example mixing of fluid flows having different viscosities used to introduce additional reaction partners, suspending solid materials, transferring heat to heat exchange elements, circulating the fluid to the surface for evaporating solvents, precipitating and crystallizing solid materials, etc.
To optimally solve the primary tasks, various stirring bodies have been previously developed, which may differ with respect to the transport direction, namely radial and/or axial, the number of stirring blades, the shape of the stirring blades and the number of stirring stages.
For example, U.S. Pat. No. 4,371,480 A and in DE 92 01 820 U1 describe stirring arrangements are disclosed wherein a gas is drawn in by the stirring body. Conversely, stirring arrangements with “external gas supply” are known, meaning that the gas is not drawn in by the stirring body, but is supplied by a blower or compressor or from a pressure reservoir. Several examples for conventional stirring arrangements will now be described.
WO 2008/083673 A2 discloses a stirring arrangement with a stirring body and a gas supply device of the aforedescribed type. This gas supply device supplies gas below or on the sides of the stirring body, wherein this gas is dispersed by the stirring body. With this design of the stirring arrangement, the gas is supplied and distributed either on the sides and/or below the stirring body at a relatively large distance from the stirring body.
EP 0 847 709 A1 discloses a stirring body which is used, in particular, as gas supply stirring body for stirring fluids. A gas, for example air, is supplied to the fluids. In this gas supply stirring body, the gas is supplied via a supply tube with a discharge port located below the stirring axis of the stirring body. Optionally, several supply tubes may be provided below and/or on the side spaced from the stirring body. The gas is supplied via these tubes to the outflow of the stirring body of the stirring arrangement.
EP 1 055 450 B1 shows a stirring arrangement, wherein the gas is supplied via co-rotating distribution elements.
As can be seen from the aforedescribed stirring arrangements, stirring arrangements having an external gas supply can be divided into two different cases.
The gas may be supplied via stationarily installed supply lines, for example via tubes arranged below the stirring body or tubes arranged on the side next to the stirring body or a ring-shape gas distributor, a so-called ring shower arranged below the stirring body. Such ring shower has several openings distributed along its circumference, through which the gas to be supplied to the stirring body can exit.
Gas can also be supplied through co-rotating distribution elements, as is the case for the stirring arrangement described in EP 1 055 450 B1. However, if the stirring body of this stirring arrangement must satisfy one of the aforementioned primary tasks in addition actually supplying the gas, the rotating distribution elements for supplying gas are arranged outside the actual stirring body, preventing an optimal gas supply.
The conventional embodiments of gas supply devices include several individual and separate components which require associated rigid supports to prevent flow-induced oscillations. It may also be necessary to use expensive materials, duplex steels, alloys or titanium to prevent corrosion. Overall, the conventional gas supply devices are therefore complex, include several components and are complex and cost-intensive to manufacture.
It is therefore an object of the invention to provide a gas supply to the stirring body of a stirring arrangement, which has a very simple structure while simultaneously attaining a significant cost reduction, and to also achieve a targeted gas discharge at any location of the stirring body or the stirring blades desired for the flow mechanics. In particular, the gas should be optimally dispersed without adversely affecting the primary task of the stirring arrangement.